Hard metal carbide products



2,971,839 Patented Feb. 14, 1961 HARD METAL CARBIDE PRODUCTS Leon Nussbaum, London, England, assignor to Titanium Products Corporation Limited, Tel Aviv, Israel No Drawing. Filed Nov. 21, 1955, Ser. No. 548,261 Claims priority, application Great Britain Dec. 2, 1954 13 Ciairns. (Cl. 75-203) This invention relates to a process for the manufacture of hard metal carbide products.

According to the process of the present invention for.

the manufacture of hard metal carbide products, at least one carbide of a hard metal is recrystallised by heating, the recrystallised product after comminution is intimately mixed wtih at least one binder metal, the mixture is heated to a temperature sufficient to convert the binder metal or metals into the liquid state and form a bindercarbide eutectic, whereafter the mixture is comminuted, pressed and sintered to form the desired products.

Any of the usual hard metal carbides may be employed, but preferably titanium carbide constitutes the whole or a predominant part of the carbide employed. Other carbides which may be used are columbium carbide, tantalum carbide, iron carbide and tungsten carbide.

Preferably the binder metal or one of the binder metals is nickel. Nickel may with advantage be employed in conjunction with one or more of the following metals: chromium, cobalt, manganese and ferro-titanium, "or alloys containing the same.

Thus, the first step of the process consists of recrystallising a single carbide or mixture of carbides from the largely amorphous condition obtained by normal carburising techniques.

This increases the percentage of combined carbon and decreases the percentage of free carbon in the carbide or carbides. At the same time, in the case of a mixture of carbides considerable mutual solution takes place. The symmetrical crystals so formed have greater abrasive properties than amorphous materials of similar compositions.

In the second step of the process the liquidbinder forms a binder-carbide eutectic from which very finely divided carbide crystals precipitate on cooling. Thus this step produces a high degree of dispersion of the binder metal or metals throughout the carbide or carhides and, when the binder consists of two ormore metals, the liquified metals satisfactorily form the alloy on which the physical properties so largely depend. The material after crushing, milling, pressing and sinteringin the usual manner produces compacts of improved physical properties.

The following examples, in which the parts and percentages are by weight, illustrate the invention.

A basic carbide mixture comprising: 1

Parts Titanium carbide 7 Tantalum/columbium carbide 1 free from the carbides of iron and manganese (the tantalum/columbium carbide constituent may vary according to the constitution of the mixed oxide constituents used) having typical carbon content assay as follows:

Percent Total carbon 17.8 Free carbon ;0.9' Combined carbon 16.9

was ball milled in carbon tetrachloride to a particle size of minus 300 mesh (B.S.S.) for about 18 hours. The milled carbides .were carefully dried and loaded into carbon boats. The loaded boats were continuously fed through a carbon tube resistance furnace with a preheated entry zone and a water-cooled exit zone, at the rate of /2" per minute and a temperature of 2600 C. in an atmosphere of dried de-ammoniated cracked ammonia. This treatment increased the amount of combined carbon and decreased the amount of free carbon and ensured the solution of the columbium, tantalum and iron carbides in the titanium carbide.

.The product of this recrystallisation process contained 17.7% total carbon, 0.2% free carbon and 17.5% combined carbon.

' The recrystallised carbides were then crushed and ball milled to a particle size of minus 100 mesh (I.M.M.)

Three binders were prepared according to the following prescription:

(1) Preparation of binder All binder metal powders to be of not less than 99.5% purity. The individual powders are mill-mixed in a carbide-lined centrifugal mill in acetone with an equivalent weight of carbide balls, for eighteen hours. The mixture is transferred to a stainless steel boat. The acetone is dried oil at a low temperature in a controlled atmosphere and cooled in the water box. Carefully granulate the dried mass and re-charge the stainless steel boats. Sinter at temperature for thirty minutes running up at the rate of 1000 C. per hour.

The three binders and their sintering temperatures are as follows:

p The binders are added in the form of the part-sintered sponge, in proportions varying from 7% to 45% according to the range of physical properties required.

In these examples the proportions were:

Percent Percent Binder 1) 15 Mixed carbides Binder (2) 30 Mixed carbides 70 Binder (3) 30 Mixed carbides 70 The mixtures were ball milled in a carbide-lined centrifugal mill and a stainless steel gravity mill in acetone until the binder metals were evenly dispersed throughout the charge by coating or smearing the carbide particles. This took about 48 hours. The milled carbide plus binder was then loaded into carbon boats and oven-dried at 65 to 82 C. The loaded boats were fed continuously through a carbon tube resistance furnace at a rate of /2" per minute at a pre-sintering temperature of 1150- 1200 C. in the case of binder (1), 1050-1150" 'C. in the case of binder (2) and 1l50-l200 C. in the .case. of binder (3). The friable mass was broken into pea-size granules. The boat was recharged with the granules and again fed through the furnace at the same rate at the homogenising temperature of 1900 C. in the case of the binder (l), 1750 C. in the case of binder (2) and 1750 C.' in the case of binder (3). Both treatments took place in an atmosphere of dried de-ammoniated cracked ammonia. During this treatment the binder melted and alloyed and permeated the spaces between the particles of the carbide and as the temperature rose formed a eutectic with the smaller particles and the surfaces of the larger until equilibrium was reached. On cooling, the dissolved carbides precipitated finely in the binder network. The homogenised mass was crushed and ball milled to 5 microns and under and used in the production of hard metal components produced by normal. technique.

Compacts made from this material show maximum density for the composition, freedom from unbonded groups of carbide particles, optimum binder dispersion and increased hardness of 1 to 2 points Rockwell A scale, and an increase in transverse rupture strength f a What I claim is:

1. A process for the manufacture of hard metal carbide products which comprises heating a mixture of a predominant quantity of titanium carbide with a subordinate quantity of tantalum and columbium carbides to a temperature of about 2600 C. to effect recrystaliisation of the carbides, comminuting the recrystallised carbides, intimately mixing the comminuted recrystallised carbides with about by weight of the resultant mixture of a binder metal composition consisting of equal quantities of chromium and nickel heating the mixture to about 1900 C. so as to convert all binder metal into the liquid state and form a binder-carbide eutectic, allowing the mixture to cool and comminuting, pressing and sintering the mixture to form the desired products.

2. A process for the manufacture of hard metal carbide products which comprises heating a mixture of a predominant quantity of titanium carbide with a subordinate quantity of tantalum and columbium carbides to a temperature of about 2600 C. to effect recrystallisation of the carbides, comminuting the recrystallised carbides, intimately mixing the comminuted recrystallised carbides with about 30% by weight of the resultant mixture of a binder metal composition consisting of about 35% by weight of manganese, about 42.5% by weight of chromium and about 22.5% byweight of nickel, heating the mixture to about 1750 C. so as to convert all binder metal into the liquid state and form a binder-carbide eutectic, allowing the mixture to cool and comminuting, pressing and sintering the mixture to form the desired products.

3. A process for the manufacture of'hard metal carbide products which comprises intimately mixing comminuted mixed crystals of hard metal carbides consistingpredominantly of titanium carbide with a subordinate quantity of at least one carbide selected from the group consisting of tantalum carbide and columbium carbide with between about 7 and about 45% by weight of the resultant mixture of a binder metal composition including nickel and at least an equal amount of chromium, heating-the mixture, the proportion of the binder metals comprising nickel and chromium to the carbides and the temperature of bides, intimately mixing the comminuted, recrystallised carbides with between about 7 to about 45% by weight of a binder metal composition including between about 22V: and about 50% of nickel and about 37/::% to about 50% of chromium, heating the mixture to between about 1750 C. and about 1900 C. to convert the binder metals into the liquid state and form a bindercarbide eutectic, allowing the mixture to cool and comminuting, pressing, and sintering the mixture to form the desired product.

5. A process for the manufacture of hard-metal carbide products which comprises mixing a comminuted recrystallized carbide material, a major portion of which consists of titanium carbide, with between about 7 and about 45 by weight of the resultant mixture of a binder material containing nickel and chromium, the chromium being present in the binder material in an amount at least equal to the nickel, heating the mixture to a temperature sufiicient to liquefy the binder material, allowing the mixture to cool, comminuting the cooled mixture, and subsequently pressing and sintering the comminuted mixture to form the desired products.

, 6. A process for the manufacture of hard metal carbide products which comprises heating a mixture of hard metal carbides consisting predominantly of titanium carbide and containing a subordinate quantity of tantalum and columbium carbides to a temperature of about 2600 C. to'eifect recrystallization of the carbides, comminuting the recrystallized carbides, intimately mixing the comminutated recrystallized carbides with about 30% by weight of the resultant mixture of a binder metal composition consisting of about 25% by weight of ferrotitanium, about 37.5% by weight of chromium and about 37.5% by weight of nickel, heating the mixture to about 1750 C. so as to convert all binder metalinto the liquid state and form a binder-carbide eutectic, allowing the mixture to cool and comminuting, pressing and sintering the mixture to form the desired products.

' 7. A process for the manufacture of hard metal carbide products which comprises intimately mixing comminuted mixed crystals of hard metal carbides consisting predominantly of titanium carbide and containing a subordinate quantity of at least one carbide selected from the group consisting of tantalum carbide and columbium carbide, with between about 7 and about 45% by weight of the resultant mixture of a binder metal composition including between about 22.5 and about 50% by weight of nickel and between about 37.5 and about 50% by weight of chromium, heating the mixture to a temperature between about 1750 C. and about 1900' C. to convert the binder metals into the liquidstate and form a binder-carbide eutectic, allowing the mixture to cool and comminuting, pressing, and sintering the mixture to form the desired product. I

8. A process for the manufacture of hard metal carbide products which comprises'intimately mixing comminuted mixed crystals of hard metal carbides consisting predominantly of titanium carbide and containing a subordinate quantity of at least one carbide selected from the group consisting of tantalum carbide and columbium carbide and at least one carbide selected from the group-consisting of iron carbide and tungsten carbide,

heating being such that the binder metals alloy with one another and form a liquid, binder-carbide eutectic with a part only of the carbides while the remainder of the carbides remain as a solid, allowing the mixture to cool to the solidification of the eutectic, comminuting the cooled mass and pressing and sintering the comminuted material to form the desired products. V

4. A process for the manufacture of hard metal carbide products which eomprisesheating a mixture .of a predominant quantity of titanium carbide with asubordinate quantity of tantalum and columbium carbidesto a temperature-to about 2600" C'.'to effect recrystallisation of the carbidesfcom'minuting the recrystallised carwith between about 7 and about 45% by weight'of the resultant mixture of a binder metal composition including between about 22.5 andabout 50% by weight of nickel and between about 37.5 and about 50% by weight of chromium, heating the mixture to a temperature between about 1750 C. and about 1900 C. to convert the binder metals into the liquid state and form a bindercarbide eutectic, allowing the mixture to cool and comminuting, pressing, and sintering the mixture to form the U desired product.

V 9. A process for the manufacture of hard metalcarbide products which comprises intimately mixing comminuted mixed crystals of hard metal carbides consisting predominantly of titanium carbide and containing a subordinate quantity of at least one carbide selected from the group consisting of tantalum carbide and columbium carbide, with between about 7 and about 45% by weight of the resultant mixture of a binder metal composition consisting of nickel powder and an at least amount of chromium powder heating the mixture to a temperature between about 1750 C. and about 1900 C. to convert' the binder metals into the liquid state and form a bindercarbide eutectic, allowing the mixture to cool and comminuting, pressing and sintering the mixture to form the desired product.

10. A process for the manufacture of hard metal carbide products which comprises intimately mixing comminuted mixed crystals of hard metal carbides consisting predominantly of titanium carbide and containing about 12.5% by weight of at least one carbide selected from the group consisting of tantalum carbide and columbium carbide, with between about 7 and about 45% by weight of the resultant mixture of a binder metal composition including between about 22.5 and about 50% by Weight of nickel powder and between about 37.5 and about 50% by weight of chromium powder, heating the mixture to a temperature between about 1750 C. and about 1900 C. to convert the binder metals into the liquid state and form a binder-carbide eutectic, allowing the mixture to cool and comminuting, pressing, and sintering the mixture to form the desired product.

11. A process for the manufacture of hard metal carbide products which comprises intimately mixing comminuted mixed crystals of hard metal carbides consisting predominantly of titanium carbide, with between about 7 and about 45% by weight of the resultant mixture of a binder metal composition including nickel powder and at least an equal amount of chromium powder, heating the mixture to a temperature between about 1750 C.

and about 1900 C. to convert the binder metals into the liquid state and form a binder-carbide eutectic, allowing the mixture to cool and comminuting, pressing, and sintering the mixture to form the desired product.

12. A process for the manufacture of hard metal carbide products which comprises intimately mixing comminuted mixed crystals of hard metal carbides consisting predominantly of titanium carbide, with between about 7 and about by weight of the resultant mixture of a binder metal composition including nickel and chromium in an amount at least equal to the nickel, and manganese, heating the mixture to a temperature between about 1750 C. and about 1900 C. to convert the binder metals into the liquid state and form a binder-carbide eutectic, allowing the mixture to cool and comminuting, pressing, and sintering the mixture to form the desired product.

13. A process as claimed in claim 12, wherein the combined amount of nickel and chromium in the binder metal composition is greater than the amount of manganese.

References Cited in the file of this patent UNITED STATES PATENTS 1,895,354 Taylor Ian. 24, 1933 2,246,387 Schwarzkopf June 17, 1941 2,356,009 Schwarzkopf Aug. 15, 1944 2,731,710 Lucas et a1 May 13, 1954 2,765,227 Goetzel et al. Oct. 2, 1956 2,791,025 Ballhousen et a1. May 7, 1957 OTHER REFERENCES Refractory Hard Metals, Schwarzkopf and Kieffer, 1953, published by the Macmillan Company, N.Y., pg. 396. Copy in Division 3.

Treatise on Powder Metallurgy, Goetzel, vol. II, 1950, pp. 108-109. Copy in Library. Copy in Division 46.

UNITED STATES PATENT OFFICE CETIFICATION 0F CORECTIQN Patent No; 2,971,839 February 14, 1961 Leon Nussbaum It is hereby certified'that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

' Column 4 line 2, for "to" read and column 5 line 6, after least" insert equal o Signed and sealed this 27th day of June 19610 (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent N0; 2,971,839 February 14, 1961 Leon Nussbaum It is hereby certified'that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below. I

Column 4, line 2, for "to" read and column 5 line 6, after "least" insert equal =0 Signed and sealed this 27th day of June 1961;

(SEA L) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

5. A PROCESS FOR THE MANUFACTURE OF HARD-METAL CARBIDE PRODUCTS WHICH COMPRISES MIXING A COMMINUTED RECRYSTALLIZED CARBIDE MATERIAL, A MAJOR PORTION OF WHICH CONSISTS OF TITANIUM CARBIDE, WITH BETWEEN ABOUT 7 AND ABOUT 45% BY WEIGHT OF THE RESULTANT MIXTURE OF A BINDER MATERIAL CONTAINING NICKEL AND CHROMIUM, THE CHROMIUM BEING PRESENT IN THE BINDER MATERIAL IN AN AMOUNT AT LEAST EQUAL TO THE NICKEL, HEATING THE MIXTURE TO A TEMPERATURE SUFFICIENT TO LIQUEFY THE BINDER MATERIAL, ALLOWING THE MIXTURE TO COOL, COMMINUTING THE COOLED MIXTURE, AND SUBSEQUENTLY PRESSING AND SINTERING THE COMMINUTED MIXTURE TO FORM THE DESIRED PRODUCTS. 